Re: [Xen-devel] [PATCH v5 8/8] x86/iommu: add map-reserved dom0-iommu option to map reserved memory ranges

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 17.08.18 at 13:17, <roger.pau@xxxxxxxxxx> wrote:
> On Fri, Aug 17, 2018 at 05:08:08AM -0600, Jan Beulich wrote:
>> >>> On 14.08.18 at 15:43, <roger.pau@xxxxxxxxxx> wrote:
>> > @@ -185,7 +219,13 @@ void __hwdom_init arch_iommu_hwdom_init(struct domain 
>> > *d)
>> >          if ( !hwdom_iommu_map(d, pfn, max_pfn) )
>> >              continue;
>> >  
>> > -        rc = iommu_map_page(d, pfn, pfn, IOMMUF_readable|IOMMUF_writable);
>> > +        if ( iommu_use_hap_pt(d) )
>> > +        {
>> > +            ASSERT(is_hvm_domain(d));
>> > +            rc = set_identity_p2m_entry(d, pfn, p2m_access_rw, 0);
>> > +        }
>> > +        else
>> > +            rc = iommu_map_page(d, pfn, pfn, 
>> > IOMMUF_readable|IOMMUF_writable);
>> 
>> Why iommu_use_hap_pt()? Shouldn't HAP with or without shared
>> page tables as well as shadow all get the same in-sync p2m and
>> IOMMU mappings?
> 
> iommu_map_page is a noop if iommu_use_hap_pt is true (see
> intel_iommu_map_page for example). Hence in the case the IOMMU page
> tables are shared with HAP the pages must be added to the p2m.

This wasn't what I'm after, while ...

> I could switch this to use set_identity_p2m_entry if the guest is
> auto-translated and only use iommu_map_page for non-autotranslated
> guests.

.... indeed this is what I would prefer (unless there a reasons
for not doing so).

Jan



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